A known tire construction uses a body ply having reinforcement elements that extend from bead portion to bead portion through opposing sidewall portions, and a crown portion of the tire. Sometimes referred to as the carcass ply or reinforcing ply, the body ply is typically anchored at the beads and maintains the overall shape of the tire as the tire is inflated and used. The reinforcement elements of the body ply are usually oriented substantially along the radial direction (a direction perpendicular to the axis of rotation) and can include e.g., a ferrous metal.
During use of the tire, these reinforcement elements (sometimes referred to as cords) may be damaged e.g., from impact with objects in the roadway, travel over curbs, and other damaging events. In some situations, the reinforcement elements may be completely broken as a result of such an event. Unfortunately, this damage may not be readily discoverable from a visual inspection of the exterior of the tire because the reinforcement elements are contained within the rubber materials used to construct the tire.
Commercial tires are commonly reused after a process referred to as retreading. With retreading, worn tread is removed from the tire and a new tread belt or tread section is installed onto the tire. Replacement of the tread is less expensive than replacing the whole tire and allows additional mileage to be obtained using the same tire carcass. This practice is common particularly with commercial tires for heavy trucks.
Before replacing the tread, however, it is advantageous to inspect the tire, including the reinforcement elements of the body ply, for damage or wear. In certain situations, inspection may reveal that replacement of the tire is required rather than retreading. Alternatively, repair of the tire may be required. As stated above, not all damage to interior elements such as e.g., the reinforcement elements of the body ply are readily apparent from a visual inspection alone.
As the reinforcement elements for commercial tires such as heavy truck tires are frequently constructed from a ferrous material, one or more sensors can be used to detect discontinuities in the reinforcement elements such as e.g., breaks that are not otherwise ascertainable from a visual inspection of the tire. For example, magnets can be used to create fields of magnetic flux along the reinforcement elements. Sensors can be used to detect changes in the magnetic flux that are indicative of a break. It is desirable to automate such an inspection process so that multiple tires may be inspected economically and expediently. It is also desirable to minimize the amount of time required for the inspection process.
Detecting damage to the reinforcement elements of the body ply along the bead portion of the tire is problematic. Each opposing bead portion of the tire typically includes a bead that extends along the circumferential direction forming a hoop or ring. This bead is constructed of ferrous metal that can interfere with accurate detection of damage to the reinforcement elements of the body ply near the bead portion of the tire. More specifically, the bead provides a substantial amount of ferrous metal that impedes the level of saturation of the reinforcement elements with magnetic flux that is desired for break detection. Some tire constructions also use a body ply that is wrapped around the bead, which further increases the amount of ferrous metal in the area where inspection is desired. Additionally, the non-linear geometry of the bead portion also impedes efforts to place the sensors close to the surface of the tire, which is desired for improved detection sensitivity and accuracy. The non-linear geometry and presence of ferrous metal also creates problems in creating fields of magnetic flux that are properly positioned at a level sufficient for damage detection but without undesirably saturating sensors used to detect the magnetic flux.
As such, a device that can be used for tire inspection along the bead portion of the tire would be useful. More particularly, a device that can repeatedly place one or more sensors near the bead portion for detection of damage to the reinforcement elements of a body ply would be useful. Such a device that can also properly create the magnetic field desired for the damage detection would be particularly beneficial.